As is known, a cover cloth stuck to a toothed belt prevents cracking of the rubber portion of the belt, protects the rubber portion, and imparts adequate strength to the tooth portion of the belt to retain its shape on engaging with a toothed pulley. Therefore, the cover cloth should adhere well to the rubber portion, and have such adaptability and durability to withstand for a long time the environment in which power transmission is conducted.
However, adhesiveness and adaptability to the environment often conflict with each other. When engaging with the toothed pulley, the surface of the tooth portion wears off. Desirably, therefore, the cover cloth stuck to the tooth surface should have abrasion resistance. Some commonly used fibers, such as nylon 6, adhere well to rubber, but have high friction coefficients. When engaging with the toothed pulley, a cover cloth with a high friction coefficient liberates heat which impairs the durability of both the rubber portion and the cover cloth.
Fluorine-based fibers have low friction coefficients, but do not adhere well to rubber. Consequently, a cover cloth of this type may come off from the tooth surface while power is being transmitted.
This invention provides a toothed belt which is free from the above-described shortcomings.
An embodiment of this invention will be described with reference to the accompanying drawings.